Failures in a vehicle-mounted lighting device have been determined (detected) on the basis of a current supplied to lamps of the lighting device. In contrast, a technique for determining failures in a lighting device on the basis of a video of the outside of a vehicle acquired with a vehicle-mounted camera has been proposed in recent times (for example, Patent Document 1). Moreover, a technique for determining failures in a lighting device on the basis of brightness around a vehicle detected by an illumination sensor and the presence or absence of detection of light of a lamp using a light guide cable has also been proposed.